BetaWolf is a scientist fascinated by physics, chemistry,  mathematics and especially the symmetry of phenomena in nature and the way humans describe them in the form of fundamental laws. He submitted to our blog a project focused on measuring water activity powered by Arduino Pro Mini :

Water activity? And why would I want to measure it? Food always contains a certain amount of ‘free’ or unbound water. The more unbound water is present, the easier it is for micro-organisms like fungi to grow. Hence, the shelf life of food products is shortened by the presence of unbound water. Water activity is a physical quantity that describes the amount of unbound water in a product. Therefore, by measuring the water activity, you can estimate the shelf life of food. Only problem is the incredible amount of money you have to pay for a commercial water activity meter. In this article I describe an easy and cheap water activity meter on the basis of a humidity sensor, an NTC, and an Arduino Pro Mini.

Check his blogpost for all the details about this project.